Smoking article with improved extinguishing characteristcs

ABSTRACT

A smoking article includes a tobacco rod and a wrapper, wherein the wrapper includes at least one zone treated with an inorganic salt providing reduced ignition propensity. Preferably, the porosity of the wrapper in the treated zones is larger than 10 CU. Suitable inorganic salts are, e.g., magnesium chloride, aluminum sulfate, alum, sodium tetraborate, the hydrated forms of these compounds, sodium chloride, or mixtures thereof.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority from European Patent Application Serial No. EP 07400034.0, filed Dec. 20, 2007, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a smoking article with improved extinguishing characteristics (reduced or lower ignition propensity or ignition proclivity) and to a method of manufacturing such a smoking article.

2. Discussion of the Prior Art

Product regulations in many countries specify that cigarettes have to fulfil certain safety standards regarding their ignition propensity. The ignition propensity of cigarettes can be measured by a standardized test method. Usually, the test defined in ASTM E 2187-04 is performed (ASTM: “American Standard for Testing and Materials”; ASTM E 2187: “Standard Test Method for Measuring the Ignition Strength of Cigarettes”; the extension “-04” refers to 2004 as the year of the last revision). According to ASTM E 2187-04, a sample of 40 cigarettes is tested under well-defined conditions, and the fraction of these cigarettes which burn their full length is called “the test result”. A safety standard specifies which test result is acceptable. For example, in Canada and some U.S. states, the acceptable test result is 25%, i.e., at least 75% of the cigarettes have to extinguish before burning their full length in order to comply with the safety standard.

The most common way to reduce the ignition propensity of cigarettes is to enhance the extinguishing characteristics by using a paper wrapper comprising spaced bands of lower porosity, which extend along the circumference of the wrapper. By these means, oxygen supply is reduced when the burning cone of the cigarette reaches a respective band, and the cigarette extinguishes when smoldering on a substrate, as described in ASTM E 2187-04. Common methods to produce such banded cigarette papers are described in EP 1 234 514 A2.

A general disadvantage of using low-porosity bands on wrapper papers is a reduced rod ventilation caused by the reduced porosity in these bands, resulting in changes of CO/NFDPM ratios to often undesired levels (CO: carbon monoxide, NFDPM: nicotine-free dry particulate matter).

The use of inorganic salts as burn retardants is commonly known, including some applications for tobacco products. Inorganic salts as such, however, have not been used for reducing ignition propensity, which is probably based on the assumption that a certain oxygen deficit is necessary to make cigarettes self-extinguish in the ASTM test cited above and that this can only be achieved by reducing the wrapper porosity to a level lower than 10 CU to 15 CU (CU: Coresta unit, permeability as measured in the tobacco industry, see CORESTA Recommend Method No. 40). In EP 1 234 514 A2, for example, ammonium phosphate is used as a burn retardant, but only in combination with additional substances, as e.g., alginates, which provide for a low porosity.

SUMMARY

The object of the invention is to provide a smoking article with reduced ignition propensity, which does not exhibit the disadvantage of a significantly reduced rod ventilation.

According to one aspect of the present invention, a smoking article is provided that includes a tobacco rod and a wrapper. The wrapper includes at least one zone treated with an inorganic salt providing reduced ignition propensity.

Another aspect of the present invention concerns a method of manufacturing a smoking article that includes a tobacco rod and a wrapper, where the wrapper includes at least one zone treated with an inorganic salt providing reduced ignition propensity. The method includes the step of applying the inorganic salt to the wrapper by a solution or a suspension.

According to an additional aspect of the present invention, a paper is provided that is formed as a wrapper for rolling a cigarette that includes a tobacco rod, wherein the wrapper is configured to radially surround the rod. The paper includes at least one zone treated with an inorganic salt providing reduced ignition propensity. The paper may be formed as a tube and may include a filter.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description of the preferred embodiments. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Various other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a perspective view of a smoking article constructed in accordance with the principles of one embodiment of the present invention, particularly depicting a wrapper with a treated zone;

FIG. 2 is a perspective view of a smoking article constructed in accordance with the principles of another embodiment of the present invention, particularly depicting a wrapper with multiple treated zones; and

FIG. 3 is a perspective view of the smoking article of FIG. 2, depicting the smoking article in an ignited condition.

The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments.

A smoking article 10 according to one embodiment of the invention comprises a tobacco rod 12 and a wrapper 14. The wrapper 14 includes at least one zone 16 treated with an inorganic salt providing reduced ignition propensity. This zone 16 can comprise the total wrapper 14. In advantageous embodiments of the invention, however, the wrapper 14 includes at least one discrete zone 18 treated with the inorganic salt, wherein the total surface area of the discrete zones 18 is smaller than the total surface area of the wrapper 14, i.e., in addition to any areas of the wrapper 14 being covered by, e.g., a tipping paper of a filter 20, there are exposed areas 22 of the wrapper 14 which are not treated with the inorganic salt.

Surprisingly, it was found that the application of inorganic salts is able to reduce the ignition propensity of the smoking article 10 without reducing the porosity of the wrapper 14 to levels as commonly required for this purpose. Thus, the invention does not rely on the main effect of a reduced porosity in the zones 18 treated with the inorganic salt.

In advantageous embodiments of the invention, the porosity of the wrapper 14 in the treated zones 18 is larger than 10 CU, preferably larger than 12 CU, or larger than 15 CU. Porosities in this range permit access of sufficient oxygen to the tobacco rod 12 in order to minimize carbon monoxide formation and provide for sufficient diffusion.

The inorganic salt can comprise, e.g., magnesium chloride, aluminum sulfate, alum, sodium tetraborate, hydrated magnesium chloride, hydrated aluminum sulfate, hydrated alum, hydrated sodium tetraborate, sodium chloride, or mixtures thereof. In the discrete zones 18 of the wrapper 14, the specific amount of the organic salt can be in the range of from 0.2 mg/cm² to 20 mg/cm², or in the range of from 0.5 mg/cm² to 5 mg/cm². Moreover, any interval limits in the range of from 0.2 mg/cm² to 20 mg/cm² are explicitly disclosed herewith. Such inorganic salts are less expensive than porosity-reducing agents like alginates.

In advantageous embodiments of the invention, there are discrete zones 18 treated with the salt(s) arranged as bands (rings) 24 extending along the circumference of the smoking article 10 and having a width, measured along the tobacco rod axis 26, of from 2 mm to 12 mm, or from 2 mm to 8 mm, or preferably of 6 mm. Generally, the provision of the inorganic salts in the bands 24 is sufficient for achieving reduced ignition propensity such that it is not required to treat the whole wrapper material with the inorganic salt, which results, e.g., in cost reduction and the possibility of an even higher porosity in the wrapper areas 22 between the discrete zones 18. Preferably, the wrapper 14 comprises at least two such bands 24 which are separated by at least 1 mm, or at least 5 mm, and preferably by at least 10 mm.

In advantageous embodiments of the invention, the smoking article 10 comprises a filter 20, and the smoking article 10 can be designed as a cigarette, wherein the wrapper 14 is a cigarette paper (which includes the possibility of manufacturing the wrapper from reconstituted tobacco).

Other embodiments of the invention relate to a paper for rolling cigarettes (RYO cigarettes; RYO: “Roll Your Own”), as well as to a paper tube (preferably a paper tube including a filter at one of its ends) for making cigarettes (MYO cigarettes; MYO: “Make Your Own”) by filling the paper tube with tobacco. In these cases, the rolling paper and the paper tube comprise, with respect to reduced ignition propensity, the features of the wrapper of a smoking article explained so far.

There are several ways of manufacturing a smoking article 10 according to the invention, in particular of applying the inorganic salts to the wrapper 14. These methods can be applied to a paper for rolling cigarettes or to a paper tube for making cigarettes in an analogue way.

In advantageous embodiments, the inorganic salt is applied to the wrapper 14 by means of a solution or suspension. To improve the solubility of the inorganic salt, such solution can be heated. Preferably, the solvent or the suspension agent comprises water.

The inorganic salt can be applied to the wrapper 14 by, e.g., printing techniques like gravure printing or inkjet printing, but also techniques like spraying or sizing. Printing techniques are very precise and can even be used online, e.g., in a cigarette making process after wrapping a continuous tobacco rod 12 with the wrapper material.

For example, the inorganic salt can be applied to the wrapper 14 by sizing in a papermaking process for providing the material of the wrapper 14. Whereas, usually, sizing is applied to the overall surface of the paper produced in a papermaking process, it is also possible to size zones of the paper only.

In another possibility, the inorganic salt is applied to the wrapper 14 immediately after a papermaking process during the cutting step of a mother reel into bobbins containing wrapper material, as usually performed in the cigarette paper industry in order to provide wrapper material suitable for use in a cigarette making machine.

When a bobbin containing ordinary wrapper material is provided, the inorganic salt can be applied to the wrapper material during a rewinding step of such bobbin. This step is performed offline, i.e., not during the usual operating steps of a cigarette making machine.

It is also possible to apply the inorganic salt to the wrapper 14 during a cigarette making process, i.e., online, either before wrapping a continuous tobacco rod 12 with the wrapper material or after wrapping a continuous tobacco rod with the wrapper material. For such applications, gravure printing and inkjet printing, which apply a solution or suspension of the inorganic salt as “ink”, are particularly suitable.

In the following, the invention is described in more detail by means of several embodiments, which are not considered as exclusive.

EXAMPLE A

In a pilot test, cigarette papers were homogeneously treated with inorganic salts, and the porosity of the respective cigarette paper was measured before the treatment and after the treatment. The porosity measurements were performed according to CORESTA Recommended Method No. 40. 1 CU (“CORESTA unit”) is the air flow (in cm³/min) through an area of the cigarette paper of 1 cm² when the pressure difference across the cigarette paper is 1 kPa. The following table shows the initial porosity (“base porosity”) of the cigarette paper, the salt and its amount applied as well as the porosity after the salt treatment (“remaining porosity”).

Remaining Base Porosity Salt Amount Porosity 35 CU Magnesium chloride (hydrate) 1.2 mg/cm² 16 CU 35 CU Aluminum sulfate (hydrate) 3.0 mg/cm² 11 CU 35 CU Sodium chloride 4.0 mg/cm² 64 CU 50 CU Aluminum sulfate (hydrate) 3.0 mg/cm² 18 CU

It is evident that the remaining porosity is larger than 10 CU in all cases and significantly larger than 10 CU in most of the cases.

EXAMPLE B

In another test, a commercial cigarette comprising a cigarette paper with a base porosity of 35 CU was homogeneously treated with an aqueous solution of sodium chloride until a weight of 4.0 mg sodium chloride per cm² was achieved.

The test result according to ASTM E 2187-04 (see above) for cigarettes treated in this way was 35%.

EXAMPLE C

The outer side (“felt side”) of a commercial cigarette paper (base porosity 35 CU) was sprayed with an aqueous solution of magnesium chloride to form treated discrete zones in band form of 6 mm width with a distance (gap width) of 20 mm on the paper. The concentration of the solution and the amount of spraying were adjusted so that a weight of 1.2 mg magnesium chloride per cm² was achieved. In other embodiments, the inner side (“wire side”) or both sides of the cigarette paper could be sprayed with the solution.

Conventional American Blend cigarettes were produced with the treated paper and tested according to ASTM E 2187-04. The test result was 13%.

EXAMPLE D

A warm (50° C.), saturated solution of aluminum sulfate was applied to the cigarette paper (porosity 50 CU) of a conventional cigarette during the cigarette making process using a gravure printing device. The gravure depth was adjusted so that a weight of 3 mg aluminum sulfate per cm² was achieved in the printed areas. The salt was applied in band-shaped discrete zones having a width of 6 mm each and a respective distance (width of untreated zones) of 20 mm.

According to ASTM E 2187-04, the test result was 20%.

The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention.

The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and access the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention set forth in the following claims. 

1. A smoking article comprising: a tobacco rod; and a wrapper, said wrapper including at least one zone treated with an inorganic salt providing reduced ignition propensity.
 2. The smoking article as claimed in claim 1, said treated zone having a porosity greater than 10 Coresta units.
 3. The smoking article as claimed in claim 1, said inorganic salt comprising at least one substance selected from the group consisting of magnesium chloride, aluminum sulfate, alum, sodium tetraborate, hydrated magnesium chloride, hydrated aluminum sulfate, hydrated alum, hydrated sodium tetraborate, and sodium chloride.
 4. The smoking article as claimed in claim 1, said inorganic salt in the treated zone of the wrapper being present in an amount having a range of from 0.2 mg/cm² to 20 mg/cm².
 5. The smoking article as claimed in claim 1, said wrapper including a plurality of discrete zones treated with the inorganic salt, said discrete zones presenting a total treated area that is smaller than the total surface area of the wrapper.
 6. The smoking article as claimed in claim 5, said discrete zones being arranged as bands extending along the circumference of the smoking article, each band having a width, measured along an axis of the tobacco rod, of from 2 mm to 12 mm.
 7. The smoking article as claimed in claim 6, said wrapper including at least two discrete zones, adjacent ones of said zones being separated by at least 1 mm.
 8. The smoking article as claimed in claim 1, said smoking article further comprising a filter.
 9. The smoking article as claimed in claim 1, wherein the smoking article is a cigarette, said wrapper being a cigarette paper.
 10. A method of manufacturing a smoking article as defined in claim 1, said method comprising the steps of: applying the inorganic salt to the wrapper by a solution or a suspension.
 11. The manufacturing method as claimed in claim 10, said solution being heated to improve the solubility of the inorganic salt.
 12. The manufacturing method as claimed in claim 10, said solution solvent or suspension agent comprising water.
 13. The manufacturing method as claimed in claim 10, said applying step including applying the inorganic salt to the wrapper by a technique selected from the group consisting of gravure printing, inkjet printing, spraying, and sizing.
 14. The manufacturing method as claimed in claim 10, said applying step including applying the inorganic salt to the wrapper by sizing in a papermaking process for providing the material of the wrapper.
 15. The manufacturing method as claimed in claim 10, further comprising the steps of: providing the material of the wrapper by a papermaking process; and cutting a mother reel into bobbins containing wrapper material, said applying step being performed immediately after said providing step and simultaneously with said cutting step.
 16. The manufacturing method as claimed in claim 10, said applying step including applying the inorganic salt to the wrapper during an offline rewinding step of a bobbin containing wrapper material.
 17. The manufacturing method as claimed in claim 10, said applying step including applying the inorganic salt to the wrapper online in a cigarette making process; and wrapping a continuous tobacco rod with the wrapper material, said applying step being performed before said wrapping step.
 18. The manufacturing method as claimed in claim 10, said applying step including applying the inorganic salt to the wrapper online in a cigarette making process; and wrapping a continuous tobacco rod with the wrapper material, said applying step being performed after said wrapping step.
 19. A paper forming a wrapper for rolling a cigarette that includes a tobacco rod, wherein the wrapper is configured to radially surround the rod, said paper comprising: at least one zone treated with an inorganic salt providing reduced ignition propensity.
 20. The paper as claimed in claim 19, said paper being formed as a tube, said tube including a filter. 